Re: st: Accessing the number of changes made by a "replace" command

[Nick Winter <nw53@cornell.edu>]

Another way at this:

  capture assert myvar == whatever
  while _rc {
        replace myvar = whatever
       capture assert myvar == whatever
  }

This avoids creating a copy of myvar . . .

--Nick Winter



At 12:21 PM 3/18/2005 -0500, you wrote:

> At 10:03 AM 3/18/2005 +0000, David Fischer wrote:
> > Hi all,
> > I am attempting to create a "while" loop that executes, amongst other 
> > things, a "replace" command on a particular variable.  I would like this 
> > loop to continue until the "replace" command cannot make any more changes 
> > to the data.  In order to do this I would like to be able to access the 
> > number of (real) changes made by the "replace" command, so that I can say 
> > something like "loop while (number of real changes)!=0".  Is there a way 
> > to do this in Stata?  I thought there might be an underscore variable 
> > that would do this, but I can't find one.
> > Thanks!
> > David Fisher.
> Coincidentally, just yesterday, I wrote to Stata Tech Support, asking 
> about this and suggesting that they provide a returned value.  It's 
> potentially under consideration, but there are some issues involved.
>
> Until then, the only way to correctly do it is ...
>  gen savedcopy = myvar  // possibly with a type inserted after -gen-
>  replace myvar = whatever...
>  count if savedcopy != myvar
> and test r(N)
--------------------------------------------------------
Nicholas Winter                           607.255.8819 t
Assistant Professor                       607.255.4530 f
Department of Government              nw53@cornell.edu e
308 White Hall            falcon.arts.cornell.edu/nw53 w
Cornell University
Ithaca, NY 14853-4601 

*
*   For searches and help try:
*   http://www.stata.com/support/faqs/res/findit.html
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/